Taking 40 winks in the middle of the day may reduce the risk of death from heart disease, particularly in young healthy men, say researchers.

A six-year Greek study found that those who took a 30-minute siesta at least three times a week had a 37% lower risk of heart-related death.

The researchers took into account ill health, age, and whether people were physically active.

Experts said napping might help people to relax, reducing their stress levels.

It is known that countries where siestas are common tend to have lower levels of heart disease, but studies have shown mixed results.

The researchers in the Greek study looked at 23,681 men and women aged between 20 and 86. The subjects did not have a history of heart disease or any other severe condition.

Participants were also asked if they took midday naps and how often, and were asked about dietary habits and physical activity.

The researchers found those who took naps of any frequency and duration had a 34% lower risk of dying from heart disease than those who did not take midday naps.

Those who took naps of more than 30 minutes three or more times a week had a 37% lower risk.

Working men

Among working men who took midday naps, there was a 64% reduced risk of death compared with a 36% reduced risk among non-working men.

There were not enough female deaths to compare figures.

The researchers said taking a siesta may reduce stress, hence the more notable finding in working men.

Lead researcher Dr Dimitrios Trichopoulos, from the Harvard School of Public Health, said: "In countries where mortality from coronary diseases is low, siesta is quite prevalent.

"There have been other studies but with equivocal results.

"This study has four advantages - it's large, prospective, limited to healthy people and we have been very careful to control for physical activity.

"The thing we can say is that it's worth studying further."

He added that if backed by other trials, taking a siesta would be an interesting way of reducing heart disease as it had no side effects.

The only important factor was that people should not reduce the amount of physical activity they did in the rest of the day.

June Davison, cardiac nurse at the British Heart Foundation, said: "These interesting findings identify that having a siesta is associated with a reduced risk of dying from a heart problem, particularly in working men.

"Having a nap in the middle of the day may help people to unwind and relax - which is important for our overall health.

"However it is important to get a balance between rest and activity, as being regularly active can help reduce the risk of coronary heart disease."

She added that people who felt stressed might be more tempted to have less healthy behaviour, such as smoking, eating a poor diet, drinking too much alcohol and not getting enough exercise. This would add to their risk of suffering a heart-related death.